diff --git a/source/java/org/alfresco/repo/domain/hibernate/ChildAssocImpl.java b/source/java/org/alfresco/repo/domain/hibernate/ChildAssocImpl.java
index 9f618b1ede..c32e0bf1b4 100644
--- a/source/java/org/alfresco/repo/domain/hibernate/ChildAssocImpl.java
+++ b/source/java/org/alfresco/repo/domain/hibernate/ChildAssocImpl.java
@@ -151,11 +151,12 @@ public class ChildAssocImpl implements ChildAssoc
             return false;
         }
         ChildAssoc that = (ChildAssoc) obj;
-        return (this.getIsPrimary() == that.getIsPrimary()
-                && EqualsHelper.nullSafeEquals(this.getTypeQName(), that.getTypeQName())
+        return (
+                   EqualsHelper.nullSafeEquals(this.getTypeQName(), that.getTypeQName())
                 && EqualsHelper.nullSafeEquals(this.getQname(), that.getQname())
                 && EqualsHelper.nullSafeEquals(this.getParent(), that.getParent())
-                && EqualsHelper.nullSafeEquals(this.getChild(), that.getChild()));
+                && EqualsHelper.nullSafeEquals(this.getChild(), that.getChild())
+               );
     }
     
     public int hashCode()
diff --git a/source/java/org/alfresco/repo/domain/hibernate/Node.hbm.xml b/source/java/org/alfresco/repo/domain/hibernate/Node.hbm.xml
index 917f39484f..b02a880151 100644
--- a/source/java/org/alfresco/repo/domain/hibernate/Node.hbm.xml
+++ b/source/java/org/alfresco/repo/domain/hibernate/Node.hbm.xml
@@ -75,54 +75,58 @@
             name="aspects"
             table="node_aspects"
             lazy="false"
+            fetch="join"
             inverse="false" 
             sort="unsorted"
-            fetch="join"
             optimistic-lock="true"
             cascade="delete" >
          <key column="node_id" not-null="true" />
          <element column="qname" type="QName" length="200"/>
       </set>
       <!-- inverse assoc to parent childassocs -->
-      <bag
+      <set
             name="parentAssocs"
-            lazy="true"
             inverse="true" 
+            lazy="true" 
+            fetch="select"
             cascade="none"
-            optimistic-lock="true"
-            fetch="select" >
+            optimistic-lock="true" >
          <key column="child_node_id" />
          <one-to-many class="org.alfresco.repo.domain.hibernate.ChildAssocImpl" />
-      </bag>
+      </set>
       <!-- inverse assoc to child childassocs -->
-      <bag
+      <set
             name="childAssocs"
             inverse="true"
             lazy="true" 
+            fetch="select"
             cascade="none"
-            optimistic-lock="true"
-            fetch="select" >
+            optimistic-lock="true" >
          <key column="parent_node_id" />
          <one-to-many class="org.alfresco.repo.domain.hibernate.ChildAssocImpl"  />
-      </bag>
+      </set>
       <!-- inverse assoc to source nodeassocs -->
-      <bag
+      <set
             name="sourceNodeAssocs"
             inverse="true" 
+            lazy="true" 
+            fetch="select"
             cascade="none"
             optimistic-lock="true" >
          <key column="target_node_id" />
          <one-to-many class="org.alfresco.repo.domain.hibernate.NodeAssocImpl" />
-      </bag>
+      </set>
       <!-- inverse assoc to target nodeassocs -->
-      <bag
+      <set
             name="targetNodeAssocs"
             inverse="true" 
+            lazy="true" 
+            fetch="select"
             cascade="none"
             optimistic-lock="true" >
          <key column="source_node_id" />
          <one-to-many class="org.alfresco.repo.domain.hibernate.NodeAssocImpl" />
-      </bag>
+      </set>
    </class>
 
    <class
@@ -145,10 +149,10 @@
             name="node"
             class="org.alfresco.repo.domain.hibernate.NodeImpl"
             column="node_id"
-            unique="false"
-            not-null="false"
+            lazy="false"
             fetch="join"
-            lazy="false" />
+            unique="false"
+            not-null="false" />
       <property name="changeTxnId" column="change_txn_id" type="string" length="56" not-null="true" />
       <property name="deleted" column="deleted" type="boolean" not-null="true" />
    </class>
@@ -165,10 +169,6 @@
       <id name="id" column="id" type="long" >
          <generator class="native" />
       </id>
-      <property name="typeQName" column="type_qname" type="QName" length="255" not-null="true" />
-      <property name="qname" column="qname" type="QName" length="255" not-null="true" />
-      <property name="isPrimary" column="is_primary" />
-      <property name="index" column="assoc_index" />
       <!-- forward assoc to parent node -->
       <many-to-one 
             name="parent"
@@ -189,6 +189,10 @@
             not-null="true" >
          <column name="child_node_id" />
       </many-to-one>
+      <property name="typeQName" column="type_qname" type="QName" length="255" not-null="true" />
+      <property name="qname" column="qname" type="QName" length="255" not-null="true" />
+      <property name="isPrimary" column="is_primary" />
+      <property name="index" column="assoc_index" />
    </class>
 
    <class
@@ -199,21 +203,27 @@
       <id name="id" column="id" type="long" >
          <generator class="native" />
       </id>
-      <property name="typeQName" column="type_qname" type="QName" length="255" not-null="true" />
-      <!-- forward assoc to source node -->
-      <many-to-one
-            name="source"
-            class="org.alfresco.repo.domain.hibernate.NodeImpl"
-            not-null="true" >
-         <column name="source_node_id" />
-      </many-to-one>
-      <!-- forward assoc to target node -->
-      <many-to-one
-            name="target"
-            class="org.alfresco.repo.domain.hibernate.NodeImpl"
-            not-null="true" >
-         <column name="target_node_id" />
-      </many-to-one>
+      <natural-id mutable="true">
+         <!-- forward assoc to source node -->
+         <many-to-one
+               name="source"
+               class="org.alfresco.repo.domain.hibernate.NodeImpl"
+               lazy="false"
+               fetch="join"
+               not-null="true" >
+            <column name="source_node_id" />
+         </many-to-one>
+         <!-- forward assoc to target node -->
+         <many-to-one
+               name="target"
+               class="org.alfresco.repo.domain.hibernate.NodeImpl"
+               lazy="false"
+               fetch="join"
+               not-null="true" >
+            <column name="target_node_id" />
+         </many-to-one>
+         <property name="typeQName" column="type_qname" type="QName" length="255" not-null="true" />
+      </natural-id>
    </class>
    
    <query name="store.GetAllStores">
diff --git a/source/java/org/alfresco/repo/domain/hibernate/NodeImpl.java b/source/java/org/alfresco/repo/domain/hibernate/NodeImpl.java
index 5bf438f904..856efe02e5 100644
--- a/source/java/org/alfresco/repo/domain/hibernate/NodeImpl.java
+++ b/source/java/org/alfresco/repo/domain/hibernate/NodeImpl.java
@@ -16,7 +16,6 @@
  */
 package org.alfresco.repo.domain.hibernate;
 
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -66,10 +65,10 @@ public class NodeImpl extends LifecycleAdapter implements Node
     public NodeImpl()
     {
         aspects = new HashSet<QName>(5);
-        sourceNodeAssocs = new ArrayList<NodeAssoc>(3);
-        targetNodeAssocs = new ArrayList<NodeAssoc>(3);
-        parentAssocs = new ArrayList<ChildAssoc>(3);
-        childAssocs = new ArrayList<ChildAssoc>(3);
+        sourceNodeAssocs = new HashSet<NodeAssoc>(5);
+        targetNodeAssocs = new HashSet<NodeAssoc>(5);
+        parentAssocs = new HashSet<ChildAssoc>(5);
+        childAssocs = new HashSet<ChildAssoc>(11);
         properties = new HashMap<QName, PropertyValue>(5);
         
         ReentrantReadWriteLock lock = new ReentrantReadWriteLock();